1. Field of the Invention
The present invention relates to an array substrate and a liquid crystal display device using the same. More particularly, the invention relates to an array substrate which prevents the short circuiting of the inner pixels and a liquid crystal display device using the same.
2. Descriptions of the Related Art
The liquid crystal display (LCD) has gradually replaced the conventional cathode ray tube display (CRT display) due to its many advantages such as thinness, light weight, low power consumption, and no radioactive pollution. Therefore, LCDs have been used in display screens of multimedia electronic products, such as notebook computers, mobile phones, digital cameras, and personal digital assistants (PDAs).
When an LCD displays an image in a mode where light comes from the backlight module and is transmitted through a color filter, the LCD is called a “transmissive type LCD”. However, the backlight module consumes a lot of power in the transmissive type LCD. The brighter the transmissive type LCD display is, the more power the backlight module consumes. Moreover, under bright environments, the displayed images are prone to interference from external light, and therefore may render the images unclear. On the contrary, a “reflective type LCD” displays an image by reflecting ambient light. Although such an LCD may save power, the LCD exhibits a poor contrast ratio and a degraded color saturation, and cannot display images clearly under dark conditions. To overcome these problems, a “transflective type LCD” is carried out as a compromise between the transmissive type LCD and the reflective type LCD. Since the transflective type LCD uses both backlight and natural or artificial light, it may be applied in many circumstances. The transflective type LCD consumes less power compared to the transmissive LCD.
The general structure of the transflective type LCD, from bottom to top, comprises a backlight panel, a lower polarizer, an array substrate, a liquid crystal layer, a color filter, an opposing electrode substrate, and an upper polarizer. The top view and three cross-sectional views of different sections are shown in FIG. 1A, FIG. 1B, FIG. 1C, and FIG. 1D, respectively. FIG. 1B is a cross-sectional view along line A-A′ in the array substrate of FIG. 1A; FIG. 1C is a cross-sectional view along line B-B′ in the array substrate of FIG. 1A; and FIG. 1D is a cross-sectional view along line C-C′ in the array substrate of FIG. 1A. As shown in FIG. 1A, an array substrate 1 comprises a substrate 101, a plurality of scan lines 103, a plurality of data lines 105, a first dielectric layer 1013, a second dielectric layer 107, an insulating layer 109, a plurality of transmissive electrode layers 111, a plurality of reflective electrode layers 113, a plurality of switching devices 117, and a third dielectric layer 135.
When producing the array substrate 1, the insulating layer 109 will be deposited above the third dielectric layer 135 (as shown in FIG. 2A) in advance to compensate for the optical path difference between the transmissive electrode layer 111 and the reflective electrode layer 113 of the array substrate 1. The reflective electrode layer 113 will be deposited above the insulating layer 109, i.e. coating (as shown in FIG. 2B). Next, a photoresist 115 will be applied on the reflective electrode layer 113 and an exposing step will be conducted to pattern the photoresist 115 (as shown in FIG. 2C). Then, a developing step will be conducted to remove unnecessary photoresist 115 (as shown in FIG. 2D), followed by etching, and, finally, removing the entire photoresist 115.
However, as shown in FIG. 2D, in the process of developing and removing the unnecessary photoresist 115, the photoresist 115 remains due to problems such as the angle of the photoresist 115 being deposited above the insulating layer 109 in the aforementioned step and the structure design of the insulating layer 109 itself. If the photoresist 115 remains, the reflective electrode layer 113′ is prone to stay in a region between two adjacent array pixel areas 121 in the following process of etching the reflective electrode layer 113 (as shown in FIG. 1A and FIG. 2E). The residual reflective electrode layer 113′ will cause the electrode to short circuit between two adjacent array pixel areas 121.
In summary, due to the bad design of existing structure, the electrode short circuiting between two array pixels will affect the productivity of LCDs. Therefore, it is important to prevent the residual of the reflective electrode, which further causes the electrode to short circuit between the two array pixels.